The invention relates to a process for the preparation of one or more atmospheric hydrocarbon oil distillates from a hydrocarbon oil residue obtained by vacuum distillation.
In the atmospheric distillation of crude mineral oil, as applied on a large scale in refineries for the preparation of atmospheric distillates, a residual oil is obtained as a by-product. To increase the yield of atmospheric distillates from a crude oil, a vacuum distillate can be separated from the said residual oil by vacuum distillation, which vacuum distillate can be converted, for instance by catalytic cracking or hydrocracking, into one or more atmospheric distillates. Just as in atmospheric distillation, a residual oil is obtained as a by-product in vacuum distillation. In some cases this residual oil is suitable for use as the starting material for the preparation of residual lubricating oil, but generally the residual oil, which as a rule contains considerable quantities of sulphur, metals and asphaltenes, is only suitable for use as a fuel oil component.
In view of the increasing demand for atmospheric distillates, attempts were made in the past to convert the vacuum residues into atmospheric distillates, for instance by catalytic cracking or hydrocracking. The use of the vacuum residues as such as the feed for these processes has serious drawbacks which preclude their application on a commercial scale. Thus, major drawbacks of, for instance, catalytic cracking of the vacuum residues are that it entails very high catalyst consumption and that because of the very high coke and gas production only a low yield of the desired atmospheric distillates is obtained. Hydrocracking of the vacuum residues involves a rapid catalyst deactivation, a high gas production and a high hydrogen consumption.
In view of the above and considering the fact that in the processing of crude mineral oil into atmospheric distillates via atmospheric distillation and vacuum distillation combined with conversion of the vacuum distillate, considerable quantities of vacuum residue are obtained as by-product, it will be clear that there is an urgent need for a process which offers the possibility of converting these vacuum residues in an economically justifiable way into distillates such as gasolines.
Since catalytic cracking and hydrocracking have proved in practice to be excellent processes for the conversion of vacuum distillates such as vacuum gas oils into atmospheric distillates such as gasolines, the applicants have carried out an investigation to find out to what extent these processes can be employed in the conversion of the above-mentioned vacuum residues. A highly suitable process has now been found employing certain combination of catalytic cracking or hydrocracking as the main operation and a catalytic hydrotreatment as a supplementary operation.